Absorbent disposable articles, such as diapers, feminine napkins and incontinence garments, employ absorbent batts to absorb body fluids, such as urine. It has generally been desirable to form a contoured batt or pad which locates more absorbent material in those areas which are subjected to higher levels of fluid loading. Various types of conventional machines have been employed to manufacture such contoured pads.
U.S. Pat. No. 4,388,056 issued June 14, 1983 to F. B. Lee, et al. discloses an apparatus for continuously forming a cyclically contoured and densified air-laid fibrous web. The web has alternately spaced narrow regions with relatively high basis weight and wide regions with relatively low basis weight. Adjustable shutter plates are configured to span a plurality of transverse plenum segments to modulate the air flow through the device.
U.S. Pat. No. 3,682,761 issued Aug. 8, 1972 to C. A. Lee, et al. discloses a device for forming an elongated air-laid web. This web has a longitudinally extending central portion and integral longitudinally extending portions flanking the central portion. This web also has a generally stepped configuration with a greater average thickness in the central portion than in the side portions. The device taught by C. A. Lee, et al. employs baffles to direct more fibrous material toward the central portion of the web, and employs a plurality of valves to increase the amount of suction through the central portion of the web to induce the formation of a greater thickness at that central portion.
U.S. Pat. No. 4,005,957 issued Feb. 1, 1977 to P. Savich discloses a device which has a screen with pockets formed therein and which is employed to manufacture fibrous pads.
U.S. Pat. No. 3,973,291 issued Aug. 10, 1976 to C. G. Kolbach discloses a method and apparatus for forming discrete fibrous pads which have contoured thickness. The method and apparatus disclosed by Kolbach employ a sequence of masks which completely block off a source of applied vacuum to all sections of each pad receiving compartment except that section in which a region of a fibrous pad having a particular weight of fibers per unit area is to be formed.
U.S. Pat. No. 4,016,628 issued Apr. 12, 1977 to C. C. Kolbach discloses a device for forming an air-laid fibrous web having a medial portion of greater basis weight than flanking end and side portions. The apparatus includes a vacuum box which has an open end underlying a discrete section of a foraminous forming surface. Vacuum connection means establish a greater pressure drop across the discrete section of the foraminous forming surface overlying the open end of the vacuum box than across the regions of the foraminous forming surface extending beyond the edges of the vacuum box.
U.S. Pat. No. 3,962,753 issued June 15, 1976 to J. W. Dunn discloses a device for forming a fibrous glass strand mat. The apparatus includes a panel having a plurality of spaced apertures located underneath a foraminous conveyor. The plate creates a back pressure and a relatively static high pressure area immediately above the conveyor. This eliminates the problem of random movement of the fibers after deposition on the conveyor, and reduces the air circulation to permit an even distribution of the fibers on the mat.
U.S. Pat. No. 4,103,058 issued July 25, 1978 to L. D. Humlicek discloses a blown microfiber web having a network of compacted high-density regions and pillowed low density regions. The web may be collected on a perforated screen so that the microfibers deposited on the land area of the screen form the compacted high density regions and microfibers deposited over the openings of the screen formed the pillowed low density regions.
Conventional devices, such as those taught by the above references, have been difficult to adjust. In particular, these devices have required complicated adjustments to moveable plate elements located inside the forming mechanism, or have required complicated arrangements of compartments and multiple vacuum suction means for providing different amounts of applied suction to selected regions of a forming screen.